比扭力

       物体转动的效果不但与力的大小有关，还与力的作用点、力的方向有关。当用同样大小的力转动圆盘时，圆盘直径大的，力臂相应较长，力矩也就大，转动效率就高；圆盘直径小的，力臂短，力矩小，转动效果就差。  

Game Of Wrist Force

       The effect of an object's rotation is related to action point and direction of an applied force besides to its magnitude.When apply a constant force on rotating a disk,the more diameter of the disk resulting in the larger arm of force and the greater moment,the higher rotation efficiency gained;it is the same the other way round.